Listen to audio recordings to practice for choir. Choose your voice part, then plug in your headphones and start listening.
If you aren't part of the Calling All Choir, you can still enjoy the app using public domain example music. Go to the menu, then choose "Development: Use sample data?"
The app is open source software. I'm grateful to Tibor Kaputa of Simple Mobile Tools, and all the contributors to the Simple Music Player on which this is based: https://github.com/SimpleMobileTools/Simple-Music-Player